In a manufacturing step of a semiconductor device, for example, as a step for peeling a resist applied on a surface of a semiconductor wafer (hereinafter referred to as “wafer”), there is known a step in which a mixed gas of an ozone gas and a vapor is supplied to a wafer accommodated in a processing vessel so that the resist is oxidized and water-solubilized by the mixed gas, and the resist is removed by a deionized water. A processing system adapted to perform such a step for processing an object to be processed includes an ozone-gas generating part for generating an ozone gas, and a vapor generating part for generating a vapor. An ozone gas and a vapor, which have been generated by the ozone-gas generating part and the vapor generating part, are mixed and then supplied into a processing vessel (for example, Patent Document 1).    Patent Document 1: JP2003-332322A